Through-silicon vias are being used in multiple die assemblies. A through-silicon via is an electrical connection that passes through the silicon substrate of a die; these can also be known as through-device vias because the electrical connection passes through the device. Through-silicon vias can be used to provide electrical connections between dies, for example, in a stacked die assembly, augmenting or replacing edge wiring. A through-silicon via can be a pass through via (e.g., providing connection through a first die to allow two second dies disposed on either side of the first die to be connected to each other). A through-silicon via can also provide a connection to circuitry on the device. Sometimes, a through-silicon via connects to internal circuitry of the device, yet does not include typical circuitry provided in an input/output cell of an integrated circuit (e.g., when the through-silicon via is to connect to internal circuitry of another die). Through-silicon vias can be of various configurations, a common configuration being that of a vertical connection through the device.
Through-silicon vias can present a number of testing challenges. For example, dies can include very high numbers of through-silicon vias which exceed the available pin counts for testers. Another difficulty can be presented by through-silicon vias which are connected to internal nodes of a die. Signals can be incompatible with a tester (e.g., due to different drive levels) or the internal node can be extremely sensitive to electrostatic discharge (e.g., when no protection circuit is included in the die).